1. Field of the Invention
The present invention relates to an ultraviolet light irradiation device having a planar UV (ultraviolet) light source, particularly, an ultraviolet light irradiation device with an array of a plurality of thin plasma tubes arranged in parallel with each other as the UV light source.
2. Description of the Related Art
Conventionally, for example, extra high pressure mercury lamps and ultraviolet fluorescent lamps are employed widely as UV light sources used for ultraviolet light irradiation devices. Particularly, extra high pressure mercury lamps are often used as the UV light sources for semiconductor exposure apparatuses that require high irradiation intensity of ultraviolet light.
On the other hand, in the field of the ultraviolet light irradiation devices for medical use, the ultraviolet fluorescent lumps are mainly used as the UV light sources. Furthermore, in JP 2004-350946 A, a flat-type ultraviolet fluorescent lump which is composed of a discharge chamber formed by sealing the peripheral portions of two glass substrates and disposed to be opposed to each other is disclosed.
However, ultraviolet light irradiation devices in which extra high pressure mercury lamps, which are point light sources, or ultraviolet fluorescent lumps, which are line light sources, are used for UV light sources have a problem in that an optically complicated configuration is necessary in order to obtain ultraviolet light with uniform irradiation intensity in the range where ultraviolet light can be irradiated. For example, an ultraviolet light irradiation device with an extra high pressure mercury lamp used for its UV light source needs to have a configuration with a complex combination of optical components such as a reflector, a lens, a diffuser plate, and a wavelength selective filter in order to convert ultraviolet light into one with uniform irradiation intensity in the range where UV light can be irradiated from the point light source.
Furthermore, an ultraviolet light irradiation device with ultraviolet fluorescent lamps used for its UV light sources needs to have a configuration in which a plurality of ultraviolet fluorescent lamps are arranged in parallel with each other and, for example, a back surface reflector and a diffuser plate are combined together, in order to convert ultraviolet light into one with uniform irradiation intensity in the range where ultraviolet light can be irradiated from the line light source.
An ultraviolet light irradiation device with a flat-type ultraviolet fluorescent lamp described in JP 2004-350946 A (U.S. Pat. No. 7,241,306) used for its UV light source does not need to have an optically complicated configuration, since a planar light source is used instead of the line light source. However, the flat-type ultraviolet fluorescent lamp has a technical difficulty to form a large discharge chamber and therefore cannot be increased in size easily. Moreover, since the flat-type ultraviolet fluorescent lamp is configured with two glass substrates disposed to be opposed to each other, it has no is flexibility and therefore cannot configure a curved emitting surface of the UV light source.
Furthermore, the extra high pressure mercury lamps or the ultraviolet fluorescent lamps have a problem in that the irradiation intensity of UV light cannot be adjusted finely in a wide range.